The death receptor Fas is expressed on lung cells where it can transduce signals that mediate diverse outcomes. We recently showed that the oxidant, hydrogen peroxide (H202) promotes clustering of Fas in mouse lung epithelial cells, and that H202 uses Fas to signal to c-Jun-N-terminal kinase, (JNK), a critical signaling module that allows cells to sense and respond to stress. The outcome of Fas signaling is not strictly apoptosis, but also including shape changes, inflammation etc. The pro-survival factor, NF-kB is activated in a prolonged fashion in airways of mice with allergic airway disease, which can counteract the pro-apoptotic effect of Fas activation. During allergic airways inflammation, the redox environment of the lung is changed towards a pro-oxidant state, and H202 is present in lungs of mice with allergic airways disease. Thus, the hypothesis to be tested in this proposal is that H202- mediated activation of JNK in lung epithelium of mice with allergic airways disease contributes airways hyper-responsiveness (AHR) and remodeling, through oxidative activation of Fas. In Specific Aim 1, we will determine whether H202 promotes JNK activation, AHR, and remodeling in mice with allergic airways disease via the use of catalase over-expressing mice, and the use of pharmacologic agents that lower H202. We will also directly administer a source of H202, to determine whether H202 is sufficient to activate JNK, and elicit AHR, and whether this requires functional Fas. In Specific Aim 2, we will determine whether Fas is oxidized and oligomerized in mice with allergic lung disease, and whether this occurs in airway epithelium, and the requirement for H202 herein. In Specific Aim 3, we will determine the requirement of airway epithelial Fas in JNK activation, AHR, and remodeling in the airways of mice with allergic airway disease by using LPR mice, which lack Fas systemically, or via the creation a CC 10-DN-Fas expressing mouse. Lastly, in Specific Aim 4 we will determine the contribution of airway epithelial JNK activation in AHR through the generation of a transgenic mouse expressing a dominant negative version of JNK1 in cells of the conducting airways, in a tetracycline inducible manner. These approaches are crucial in defining critical oxidant targets and epithelial signaling events crucial to the patho-physiology of allergic airways disease.